The sting: did gang really use a laser, phone and a computer to take the Ritz for £1.3m?

The casino at the Ritz, to be found beneath the pavements of Piccadilly, London, in the hotel's former ballroom, prides itself on its gilded Edwardian splendour. Clients descending the staircase into the main room before perhaps heading for the discreet salle privée must feel they are slipping into a bygone era.

So it was rather incongruous that these settings were allegedly targeted for a thoroughly modern million-pound scam. Detectives are investigating claims that a gang used a laser scanner hidden in a mobile phone and linked to a computer to help beat the roulette wheel.

Two men and a woman were able, it is claimed, to place their bets in the area the computer had pinpointed as the ball's most likely resting place.

Scotland Yard sources yesterday described the case as "extremely complex". Specialised detectives from the Met's serious and organised crime group are working hard to puzzle out how the alleged scam might have worked. It is a sign of how untested this area of gambling is that no one can say whether an offence has been committed. The laws which cover gaming date back to the mid 19th century - when the possibility of such sophisticated scams were undreamed of.

It is understood that the three suspects, two Serbian men aged 38 and 33, and a 32-year-old Hungarian woman, made two visits to the casino earlier this month. On the first night they walked out with £100,000. They returned on a subsequent evening and appeared to disprove Albert Einstein's conclusion - that the only way to win on roulette was to pocket the money when the dealer was not looking - by walking out with £1.2m.

The casino is believed to have paid them £300,000 in cash and written out a cheque for the balance. But, as is routine when such big wins occur, the casino reviewed its security tapes and called in the police.

Scotland Yard confirmed that when police arrested the three at a hotel they seized a "significant quantity of cash". Officers are also thought to have confiscated a number of mobile phones. The three were bailed until the end of the month.

It is thought the gang's success may have been based on a theory known as "sector targeting". The theory is relatively simple. A player determines the point at which the ball is released and the point it passes after one or two spins. He or she can use these figures to calculate the ball's "decaying orbit" and so anticipate the area of the wheel - or sector - the ball is likely to come to rest in.

The system cannot reliably predict the slot the ball is likely to fall in but by determining the sector greatly sways the odds in the favour of the punter. The problem is that it is almost impossible to do such a calculation using mental arithmetic.

In the early eighties a gambling expert, Scott Lang, published a book detailing how to use a digital stopwatch to calculate the sector the ball would finish in but casinos simply banned stopwatches.

For years there have been rumours that con artists have made sector targeting a practical method by using computers. The data relating to the two points is fed into a computer which has been programmed to calculate the "decaying orbit".

In laboratory conditions it has been done but managing it in a casino with hundreds of thousands of pounds - and the threat of being caught - makes it much more difficult.

It is thought that the gang which allegedly struck at the Ritz may have taken the theory a step further by using the laser scanner to calculate the speed of the ball with more precision.

They would still have had to have got the information back and laid their bets within seconds - an impressive feat which, if proved, will send shock waves around the gambling houses of the world. But whether the three would be brought before a court is a moot point.

Section 17 of the Gaming Act 1845 forbids "unlawful devices". However in previous cases suspects have been able to argue that they had not interfered with a game, simply used a system to win.

The government is in the process of introducing new gambling laws which it hopes will make clearer what constitutes cheating at casinos and other places where gambling takes place.

Mark Griffiths, Europe's only professor of gambling, said: "On roulette mathematical systems have been used for years. When you've got technology involved it improves the chances."

Not all experts were convinced. Tom Kavanagh, secretary of the Gaming Board for Great Britain, the regulator for casinos, said: "Over the years we've heard about clever devices. I can't say I've ever known them to work."

In its publicity material the Ritz appears to encourage roulette players with a plan, saying the "Queen of casino games" is "ideally suited to the 'system' players". It may have been proved all too correct.

How the plan might work

1 A laser scanner hidden in a mobile phone which measures velocity is aimed at a roulette wheel as it is spun by the croupier.

2 The laser measures the speed of the ball as it is released and as it passes a second point. The ball's "decaying orbit" can be calculated.

3 The two figures are relayed to a computer, which works out where the ball is likely to come to rest. It would almost certainly not be able to predict the slot but may have been able to work out the sector, improving the odds for the gambler.

4 The computer's prediction is relayed back to the mobile phone. The bet or bets are placed before the cut-off point of three turns of the roulette wheel. The whole operation takes two or three seconds.